The present invention relates to a chain for friction pulley transmissions in which the chain circulates between pairs of friction pulleys arranged on drive-input and drive-output shafts, respectively, one pulley of each pair being formed as a cone pulley and the other pulley as a friction pulley having a friction surface which is radial or flatly conical in relation to the cone pulley.
Chains of the type to which the invention is directed include thrust pieces extending substantially transversely of the longitudinal direction of the chain for effecting friction force transmission between the friction pulleys and the chain. The end faces of these thrust pieces abut against the friction pulleys.
Such chains are known in many forms. Thus, by way of example, U.S. Pat. No. 3,089,346 describes a chain the links of which are formed by packs of side bars while either the thrust pieces pass through the packs of side bars between the articulations or the joint pieces themselves function as thrust pieces. Forms of construction similar thereto are disclosed in U.S. Pat. Nos. 3,364,767; 3,353,421; and 3,916,709.
Another form of construction is disclosed in FRG Auslegeschrift (Published Application) No. 2,116,930. There the basic body of a looping means is formed by steel strips which are joined in a closed loop to one another and onto which thrust pieces are fitted in the form of transverse members.
Thus, the invention relates to all chains with thrust pieces for friction force transmission. Only the so-called ring roller chains, such as are disclosed, for example, in German Gebrauchsmuster (Utility Model Patent) No. 1,979,429 are to be excluded.
In the known chains, the thrust pieces, seen in the radial direction, have domed end faces which are of like formation at both ends of the thrust pieces. Thus, in friction pulley transmissions with a cone pulley and a friction pulley differing therefrom with respect to the inclination of its friction face, different contact areas occur between the friction pulleys and chain, or an asymmetric pulley V-gap results. This results in a reduction of the transmittable power in comparison with those transmissions where the two friction pulleys of a pair are formed as cone pulleys of like configuration. On the other hand, in many cases it is of interest to use a friction pulley transmission of the initially stated type in order to conform to space limitations. The type of use encountered most frequently involves so-called two-belt transmissions where the two outer pulleys, in the direction of the axis of the associated shaft, of a pulley set are formed as cone pulleys while the middle pulley has a friction surface which is radial or flatly conical in relation to each cone pulley.